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Versions: (draft-liu-bonica-v6ops-dhcpv6-slaac-problem) 00 01 02 03 04 05 06 07

V6OPS                                                             B. Liu
Internet-Draft                                                  S. Jiang
Intended status: Informational                       Huawei Technologies
Expires: February 18, 2017                                       X. Gong
                                                                 W. Wang
                                                         BUPT University
                                                                  E. Rey
                                                               ERNW GmbH
                                                         August 17, 2016


   DHCPv6/SLAAC Interaction Problems on Address and DNS Configuration
                draft-ietf-v6ops-dhcpv6-slaac-problem-07

Abstract

   The IPv6 Neighbor Discovery (ND) Protocol includes an ICMPv6 Router
   Advertisement (RA) message.  The RA message contains three flags,
   indicating the availability of address auto-configuration mechanisms
   and other configuration such as DNS-related configuration.  These are
   the M, O, and A flags, which by definition are advisory, not
   prescriptive.

   This document describes divergent host behaviors observed in popular
   operating systems.  It also discusses operational problems that the
   divergent behaviors might cause.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on February 18, 2017.








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Copyright Notice

   Copyright (c) 2016 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  The M, O and A Flags  . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Flags Definition  . . . . . . . . . . . . . . . . . . . .   4
     2.2.  Flags Relationship  . . . . . . . . . . . . . . . . . . .   4
   3.  Behavior Ambiguity Analysis . . . . . . . . . . . . . . . . .   4
   4.  Observed Divergent Host Behaviors . . . . . . . . . . . . . .   6
     4.1.  Divergent Behavior on Address Auto-Configuration  . . . .   6
     4.2.  Divergent Behavior on DNS Configuration . . . . . . . . .   7
   5.  Operational Problems  . . . . . . . . . . . . . . . . . . . .   9
     5.1.  Standalone Stateless DHCPv6 Configuration not available .   9
     5.2.  Renumbering Issues  . . . . . . . . . . . . . . . . . . .   9
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  10
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  11
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  11
   Appendix A.  Test Results . . . . . . . . . . . . . . . . . . . .  12
     A.1.  Test Set 1  . . . . . . . . . . . . . . . . . . . . . . .  12
       A.1.1.  Test Environment  . . . . . . . . . . . . . . . . . .  12
       A.1.2.  Address Auto-configuration Behavior in the Initial
               State . . . . . . . . . . . . . . . . . . . . . . . .  12
       A.1.3.  Address Auto-configuration Behavior in State
               Transitions . . . . . . . . . . . . . . . . . . . . .  13
     A.2.  Test Set 2  . . . . . . . . . . . . . . . . . . . . . . .  15
       A.2.1.  Test Environment  . . . . . . . . . . . . . . . . . .  15
       A.2.2.  Address/DNS Auto-configuration Behavior of Using Only
               One IPv6 Router and a DHCPv6 Server . . . . . . . . .  15
       A.2.3.  Address/DNS Auto-configuration Behavior of Using Two
               IPv6 Router and a DHCPv6 Server . . . . . . . . . . .  19
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  22



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1.  Introduction

   IPv6 [RFC2460] hosts could invoke Neighbor Discovery (ND) [RFC4861]
   to to discover which auto-configuration mechanisms are available to
   them.  There are two auto-configuration mechanisms in IPv6:

   o  DHCPv6 [RFC3315]

   o  Stateless Address Autoconfiguration (SLAAC) [RFC4862]

   ND specifies an ICMPv6-based [RFC4443] Router Advertisement (RA)
   message.  Routers periodically multicast the RA messages to all on-
   link nodes.  They also unicast RA messages in response to
   solicitations.  The RA message contains (but not limited to):

   o  an M (Managed) flag, indicating that addresses are available from
      DHCPv6 or not

   o  an O (OtherConfig) flag, indicating that other configuration
      information (e.g., DNS-related information) is available from
      DHCPv6 or not

   o  zero or more Prefix Information (PI) Options

         an A (Autonomous) flag is included, indicating that the prefix
         can be used for SLAAC or not

   The M and O flags are advisory, not prescriptive.  For example, the M
   flag indicates that addresses are available from DHCPv6, but It does
   not indicate that hosts are required to acquire addresses from
   DHCPv6.  Similar statements can be made about the O flag.  (A flag is
   also advisory by definition in standard, but it is quite prescriptive
   in implementations according to the test results in the appendix.)

   Because of the advisory definition of the flags, in some cases
   different operating systems appear divergent behaviors.  This
   document analyzes possible divergent host behaviors might happen
   (most of the possible divergent behaviors are already observed in
   popular operating systems) and the operational problems might caused
   by divergent behaviors.

2.  The M, O and A Flags

   This section briefly reviews how the M, O and A flags are defined in
   ND[RFC4861] and SLAAC[RFC4862].






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2.1.  Flags Definition

   o  M (Managed) Flag

         As decribed in [RFC4861], "When set, it indicates that
         addresses are available via Dynamic Host Configuration
         Protocol".

   o  O (Otherconfig) Flag

         "When set, it indicates that other configuration information is
         available via DHCPv6.  Examples of such information are DNS-
         related information or information on other servers within the
         network."  [RFC4861]

         "If neither M nor O flags are set, this indicates that no
         information is available via DHCPv6" . [RFC4861]

   o  A (Autonomous) Flag

         A flag is defined in the PIO, "When set indicates that this
         prefix can be used for stateless address configuration as
         specified in [RFC4862].".

2.2.  Flags Relationship

   Per [RFC4861], "If the M flag is set, the O flag is redundant and can
   be ignored because DHCPv6 will return all available configuration
   information.".

   There is no explicit description of the relationship between A flag
   and the M/O flags.

3.  Behavior Ambiguity Analysis

   The ambiguity of the flags definition means that when interpreting
   the same messages, different hosts might behave differently.  The
   ambiguity space is analyzed as the following aspects.

   1) Dependency between DHCPv6 and RA

      In standards, behavior of DHCPv6 and Neighbor Discovery protocols
      is specified respectively.  But it is not clear that whether there
      should be any dependency between them.  More specifically, it is
      unclear whether RA (with M=1) is required to trigger DHCPv6; in
      other words, It is unclear whether hosts should initiate DHCPv6 by
      themselves if there are no RAs at all.




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   2) Overlapping configuration between DHCPv6 and RA

      When address and DNS configuration are both available from DHCPv6
      and RA, it is not clear how to deal with the overlapping
      information.  Should the hosts accept all the information?  If the
      information conflicts, which one should take higher priority?

      For DNS configuration, [RFC6106] clearly specifies "In the case
      where the DNS options of RDNSS and DNSSL can be obtained from
      multiple sources, such as RA and DHCP, the IPv6 host SHOULD keep
      some DNS options from all sources" and "the DNS information from
      DHCP takes precedence over that from RA for DNS queries"
      (Section 5.3.1 of [RFC6106]).  But for address configuration,
      there's no such guidance.

   3) Interpretation on Flags Transition

   -  Impact on SLAAC/DHCPv6 on and off

         When flags are in transition, e.g. the host is already SLAAC-
         configured, then M flag changes from FALSE to TRUE, it is not
         clear whether the host should start DHCPv6 or not; or vise
         versa, the host is already configured by both SLAAC and DHCPv6,
         then M flag change from TRUE to FALSE, it is also not clear
         whether the host should turn DHCPv6 off or not.

   -  Impact on address lifetime

         When one address configuration method is off, that is, the A
         flag or M flag changes from TRUE to FALSE, it is not clear
         whether one host should immediately release the corresponding
         address or just retain it until the lifetime expires.

   4) Relationship between the Flags

      As described above, the relationship between A flag and M/O flags
      is unspecified.

      It could be reasonably deduced that M flag should be independent
      from A flag.  In other words, the M flag only cares DHCPv6 address
      configuration, while the A flag only cares SLAAC.

      But for A flag and O flag, ambiguity could possibly happen.  For
      example, when A is FALSE (when M is also FALSE) and O is TRUE, it
      is not clear whether the host should initiate a stand-alone
      stateless DHCPv6 session.





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   Divergent behaviors on all these aspects have been observed among
   some popular operating systems as described in Section 4 below.

4.  Observed Divergent Host Behaviors

   The authors tested several popular operating systems in order to
   determine what behaviors the M, O and A flag elicit.  In some cases,
   the M, O and A flags elicit divergent behaviors.  The table below
   characterizes those cases.  For test details, please refer to
   Appendix A.

   Operation diverges in two ways: one is regarding to address auto-
   configuration; the other is regarding to DNS configuration.

4.1.  Divergent Behavior on Address Auto-Configuration

   Divergence 1-1

   o  Host state: has not acquired any addresses.

   o  Input: no RA.

   o  Divergent Behavior

         1) Acquiring addresses from DHCPv6.

         2) No DHCPv6 action.

   Divergence 1-2

   o  Host state: has acquired addresses from DHCPv6 only (M = 1).

   o  Input: RA with M =0.

   o  Divergent Behavior

         1) Releasing DHCPv6 addresses immediately.

         2) Releasing DHCPv6 addresses when they expire.

   Divergence 1-3

   o  Host state: has acquired addresses from SLAAC only (A=1).

   o  Input: RA with M =1.

   o  Divergent Behavior




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         1) Acquiring DHCPv6 addresses immediately.

         2) Acquiring DHCPv6 addresses only if their SLAAC addresses
         expire and cannot be refreshed.

4.2.  Divergent Behavior on DNS Configuration

   Divergence 2-1

   o  Host state: has not acquired any addresses or information.

   o  Input: RA with M=0, O=1, no RDNSS; and a DHCPv6 server on the same
      link providing RDNSS (regardless of address provisioning).

   o  Divergent Behavior

         1) Acquiring RDNNS from DHCPv6, regardless of the A flag
         setting.

         2) Acquiring RDNNS from DHCPv6 only if A=1.

   Divergence 2-2

   (This divergence is only for those operations systems which
   support[RFC6106].)

   o  Host state: has not acquired any addresses or information.

   o  Input: RA with M=0/1, A=1, O=1 and an RDNSS is advertised; and a
      DHCPv6 server on the same link providing IPv6 addresses and RDNSS.

   o  Divergent Behavior

         1) Getting RDNSS from both the RAs and the DHCPv6 server, and
         the RDNSS obtained from the router has a higher priority.

         2) Getting RDNSS from both the RAs and the DHCPv6 server, but
         the RDNSS obtained from the DHCPv6 server has a higher
         priority.

         3) Getting RDNSS from the router, and a "domain search list"
         information only from the DHCPv6 server(no RDNSS).

   Divergence 2-3

   (This divergence is only for those operations systems which
   support[RFC6106].)




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   o  Host state: has acquired address and RDNSS from the first router's
      RAs (M=0, O=0, PIO with A=1, and RDNSS advertised).

   o  Input: another router advertising M=1, O=1, no prefix information;
      and a DHCPv6 server on the same link providing IPv6 addresses and
      RDNSS.

   o  Divergent Behavior

         1) Never getting any information (neither IPv6 address nor
         RDNSS) from the DHCPv6 server.

         2) Getting an IPv6 address and RDNSS from the DHCPv6 server
         while retaining the address and RDNSS obtained from the RAs of
         the first router.

            (More details: the RDNSS obtained from the first router has
            a higher priority; when they receive again RAs from the
            first router, they lose/forget the information (IPv6 address
            and RDNSS) obtained from the DHCPv6 server.)

   Divergence 2-4

   (This divergence is only for those operations systems which
   support[RFC6106].)

   o  Host state: has acquired address and RDNSS from the DHCPv6 server
      indicated by the first router (M=1, O=1, no PIO or RDNSS
      advertised).

   o  Input: another router advertising M=0, O=0, PIO with A=1, and
      RNDSS.

   o  Divergent Behavior

         1) Getting address and RDNSS from the second router's RAs, and
         releasing the IPv6 address and the RDNSS obtained from the
         DHCPv6 server.

            (More details: when receiving RAs from the first router
            again, it performs the DHCPv6 Confirm/Reply procedure and
            gets an IPv6 address and RDNSS from the DHCPv6 server while
            retaining the ones obtained from the RAs of the second
            router.  Moreover, the RDNSS from router 1 has higher
            priority than the one from DHCPv6.)

         2) Getting address and RDNSS from the second router's RAs, and
         retaining the IPv6 address and the "Domain Search list"



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         obtained from the DHCPv6 server.  (It did not get the RDNSS
         from the DHCPv6 server, as described in Divergence 2-2.)

            (More details: when receiving RAs from the first router
            again, there is no change; all the obtained information is
            retained.)

         3) Getting address but no RDNSS from the second router's RAs,
         and also retaining the IPv6 address and the RDNSS obtained from
         the DHCPv6 server.

            (More details: when receiving RAs from the first router
            again, there is no change; all the obtained information is
            retained.)

5.  Operational Problems

   This section is not a full collection of the potential problems.  It
   is some operational issues that the authors could see at current
   stage.

5.1.  Standalone Stateless DHCPv6 Configuration not available

   It is impossible for some hosts to acquire stateless DHCPv6
   configuration unless addresses are acquired from either DHCPv6 or
   SLAAC (Which requires M flag or A flag is TURE).

5.2.  Renumbering Issues

   According to [RFC6879] a renumbering exercise can include the
   following steps:

   o  Causing a host to

         release the SLAAC address and acquire a new address from
         DHCPv6; or vice-versa.

         release the current SLAAC address and acquire another new SLAAC
         address (might comes from different source).

         retain current SLAAC or DHCPv6 address and acquire another new
         address from DHCPv6 or SLAAC.

   Ideally, these steps could be initiated by multicasting RA messages
   onto the link that is being renumbered.  Sadly, this is not possible,
   because the RA messages may elicit a different behavior from each
   host.




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6.  Security Considerations

   An attacker, without having to install a rogue router, can install a
   rogue DHCPv6 server and provide IPv6 addresses to Windows 8.1
   systems.  This can allow her to interact with these systems in a
   different scope, which, for instance, is not monitored by an IDPS
   system.

   If an attacker wants to perform MiTM (Man in The Middle) using a
   rogue DNS while legitimates RAs with the O flag set are sent to
   enforce the use of a DHCPv6 server, the attacker can spoof RAs with
   the same settings with the legitimate prefix (in order to remain
   undetectable) but advertising the attacker's DNS using RDNSS.  In
   this case, Fedora 21, Centos 7 and Ubuntu 14.04 will use the rogue
   RDNSS (advertised by the RAs) as a first option.

   Fedora 21 and Centos 7 behaviour cannot be explored for a MiTM attack
   using a rogue DNS information either, since the one obtained by the
   RAs of the first router has a higher priority.

   The behaviour of Fedora 21, Centos 7 and Windows 7 can be exploited
   for DoS purposes.  A rogue IPv6 router not only provides its own
   information to the clients, but it also removes the previous obtained
   (legitimate) information.  The Fedora and Centos behaviour can also
   be exploited for MiTM purposes by advertising rogue RDNSS by RAs
   which include RDNSS information.

   (Note: the security considerations for specific operating systems are
   based on the detailed test results as described in Appendix A.)

7.  IANA Considerations

   This draft does not request any IANA action.

8.  Acknowledgements

   The authors wish to acknowledge BNRC-BUPT (Broad Network Research
   Centre in Beijing University of Posts and Telecommunications) for
   their testing efforts.  Special thanks to Xudong Shi, Longyun Yuan
   and Xiaojian Xue for their extraordinary effort.

   Special thanks to Ron Bonica who made a lot of significant
   contribution to this draft, including draft editing and presentations
   which dramatically improved this work.

   The authors also wish to acknowledge Brian E Carpenter, Ran Atkinson,
   Mikael Abrahamsson, Tatuya Jinmei, Mark Andrews and Mark Smith for
   their helpful comments.



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9.  References

9.1.  Normative References

   [RFC2460]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,
              December 1998, <http://www.rfc-editor.org/info/rfc2460>.

   [RFC4443]  Conta, A., Deering, S., and M. Gupta, Ed., "Internet
              Control Message Protocol (ICMPv6) for the Internet
              Protocol Version 6 (IPv6) Specification", RFC 4443,
              DOI 10.17487/RFC4443, March 2006,
              <http://www.rfc-editor.org/info/rfc4443>.

   [RFC4861]  Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
              "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
              DOI 10.17487/RFC4861, September 2007,
              <http://www.rfc-editor.org/info/rfc4861>.

   [RFC4862]  Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
              Address Autoconfiguration", RFC 4862,
              DOI 10.17487/RFC4862, September 2007,
              <http://www.rfc-editor.org/info/rfc4862>.

   [RFC6106]  Jeong, J., Park, S., Beloeil, L., and S. Madanapalli,
              "IPv6 Router Advertisement Options for DNS Configuration",
              RFC 6106, DOI 10.17487/RFC6106, November 2010,
              <http://www.rfc-editor.org/info/rfc6106>.

9.2.  Informative References

   [RFC3315]  Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins,
              C., and M. Carney, "Dynamic Host Configuration Protocol
              for IPv6 (DHCPv6)", RFC 3315, DOI 10.17487/RFC3315, July
              2003, <http://www.rfc-editor.org/info/rfc3315>.

   [RFC3736]  Droms, R., "Stateless Dynamic Host Configuration Protocol
              (DHCP) Service for IPv6", RFC 3736, DOI 10.17487/RFC3736,
              April 2004, <http://www.rfc-editor.org/info/rfc3736>.

   [RFC6879]  Jiang, S., Liu, B., and B. Carpenter, "IPv6 Enterprise
              Network Renumbering Scenarios, Considerations, and
              Methods", RFC 6879, DOI 10.17487/RFC6879, February 2013,
              <http://www.rfc-editor.org/info/rfc6879>.







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Appendix A.  Test Results

   The authors from two orgnizations tested different scenarios
   independent of each other.  The following text decribes the two test
   sets respectively.

A.1.  Test Set 1

A.1.1.  Test Environment

   The test environment was replicated on a single server using VMware.
   For simplicity of operation, only one host was run at a time.
   Network elements were as follows:

   o  Router: Quagga 0.99-19 soft router installed on Ubuntu 11.04
      virtual host

   o  DHCPv6 Server: Dibbler-server installed on Ubuntu 11.04 virtual
      host

   o  Host 1: Window 7 / Window 8.1 Virtual Host

   o  Host 2: Ubuntu 14.04 (Linux Kernel 3.12.0) Virtual Host

   o  Host 3: Mac OS X v10.9 Virtual Host

   o  Host 4: IOS 8.0 (model: Apple iPhone 5S, connected via wifi)

A.1.2.  Address Auto-configuration Behavior in the Initial State

   The bullet list below describes host behavior in the initial state,
   when the host has not yet acquired any auto-configuration
   information.  Each bullet item represents an input and the behavior
   elicited by that input.

   o  A=0, M=0, O=0

      *  Windows 8.1 acquired addresses and other information from
         DHCPv6.

      *  All other hosts acquired no configuration information.

   o  A=0, M=0, O=1

      *  Windows 8.1 acquired addresses and other information from
         DHCPv6.





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      *  Windows 7, OSX 10.9 and IOS 8.0 acquired other information from
         DHCPv6.

      *  Ubuntu 14.04 acquired no configuration information.

   o  A=0, M=1, O=0

      *  All hosts acquired addresses and other information from DHCPv6.

   o  A=0, M=1, O=1

      *  All hosts acquired addresses and other information from DHCPv6.

   o  A=1, M=0, O=0

      *  Windows 8.1 acquired addresses from SLAAC and DHCPv6.  It also
         acquired non-address information from DHCPv6.

      *  All the other host acquired addresses from SLAAC

   o  A=1, M=0, O=1

      *  Windows 8.1 acquired addresses from SLAAC and DHCPv6.  It also
         acquired other information from DHCPv6.

      *  All the other hosts acquired addresses from SLAAC and other
         information from DHCPv6.

   o  A=1, M=1, O=0

      *  All hosts acquired addresses from SLAAC and DHCPv6.  They also
         acquired other information from DHCPv6.

   o  A=1, M=1, O=1

      *  All hosts acquired addresses from SLAAC and DHCPv6.  They also
         acquired other information from DHCPv6.

   As showed above, four inputs result in divergent behaviors.

A.1.3.  Address Auto-configuration Behavior in State Transitions

   The bullet list below describes behavior elicited during state
   transitions.  The value x can represents both 0 and 1.

   o  Old state (M = x, O = x, A = 1) , New state (M = x, O = x, A = 0)
      (This means a SLAAC-configured host, which is regardless of DHCPv6
      configured or not, receiving A in transition from 1 to 0. )



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      *  All the hosts retain SLAAC addresses until they expire

   o  Old state (M = 0, O = x, A = 1), New state (M = 1, O = x, A = 1)
      (This means a SLAAC-only host receiving M in transition from 0 to
      1.)

      *  Windows 7 acquires addresses from DHCPv6, immediately.

      *  Ubuntu 14.04/OSX 10.9/IOS 8.0 acquires addresses from DHCPv6
         only if the SLAAC addresses are allowed to expire

      *  Windows 8.1 was not tested because it always acquire addresses
         from DHCPv6 regardless of the M flag setting.

   o  Old state (M = 1, O = x, A = x), New state (M = 0, O = x, A = x)
      (This means a DHCPv6-configured host receiving M in transition
      from 1 to 0.)

      *  Windows 7 immediately released the DHCPv6 address

      *  Windows 8.1/Ubuntu 14.04/OSX 10.9/IOS 8.0 keep the DHCPv6
         addresses until they expire

   o  Old state (M = 1, O = x, A = 0), New state (M = 1, O = x, A = 1)
      (This means a DHCPv6-only host receiving A in transition from 0 to
      1.)

      *  All host acquire addresses from SLAAC

   o  Old state (M = 0, O = 1, A = x), New state (M = 1, O = 1, A = x)
      (This means a Stateless DHCPv6-configured host [RFC3736], which is
      regardless of SLAAC configured or not, receiving M in transition
      from 0 to 1 with keeping O=1 )

      *  Windows 7 acquires addresses and refreshes other information
         from DHCPv6

      *  Ubuntu 14.04/OSX 10.9/IOS 8.0 does nothing

      *  Windows 8.1 was not tested because it always acquire addresses
         from DHCPv6 regardless of the M flag setting.

   o  Old state (M = 1, O = 1, A = x), New state (M = 0, O = 1, A = x)
      (This means a Stateful DHCPv6-configured host, which is regardless
      of SLAAC configured or not, receiving M in transition from 0 to 1
      with keeping O=1 )





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      *  Windows 7 released all DHCPv6 addresses and refreshes all
         DHCPv6 other information.

      *  Windows 8.1/Ubuntu 14.04/OSX 10.9/IOS 8.0 does nothing

A.2.  Test Set 2

A.2.1.  Test Environment

   This test was built on real devices.  All the devices are located on
   the same link.

   o  A DHCPv6 Server and specifically, a DHCP ISC Version 4.3.1
      installed in CentOs 6.6.  The DHCPv6 server is configured to
      provide both IPv6 addresses and RDNSS information.

   o  Two routers Cisco 4321 using Cisco IOS Software version 15.5(1)S.

   o  The following OS as clients:

      *  Fedora 21, kernel version 3.18.3-201 x64

      *  Ubuntu 14.04.1 LTS, kernel version 3.13.0-44-generic (rdnssd
         packet installed)

      *  CentOS 7, kernel version 3.10.0-123.13.2.el7

      *  Mac OS-X 10.10.2 Yosemite 14.0.0 Darwin

      *  Windows 7

      *  Windows 8.1

A.2.2.  Address/DNS Auto-configuration Behavior of Using Only One IPv6
        Router and a DHCPv6 Server

   In these scenarios there is two one router and, unless otherwise
   specified, one DHCPv6 server on the same link.  The behaviour of the
   router and of the DHCPv6 server remain unchanged during the tests.

   Case 1: One Router with the Management Flag not Set and a DHCPv6
   Server

   o  Set up

      *  One IPv6 Router with M=0, A=1, O=0 and an RDNSS is advertised





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      *  A DHCPv6 server on the same link advertising IPv6 addresses and
         RDNSS

   o  Results

      *  Fedora 21, MAC OS-X, CentOS 7 and Ubuntu 14.04 get an IPv6
         address and an RDNSS from the IPv6 router only.

      *  Windows 7 get an IPv6 address from the router only, but they do
         not get any DNS information, neither from the router nor from
         the DHCPv6 server.  They also do not get IPv6 address from the
         DHCPv6 server.

      *  Windows 8.1 get an IPv6 address from both the IPv6 router and
         the DHCPv6 server, despite the fact that the Management flag
         (M) is not set.  They get RDNSS information from the DHCPv6
         only.

   Case 2: One Router with Conflicting Parameters and a DHCPv6 Server

   o  Set up

      *  One IPv6 Router with M=0, A=1, O=1 and an RDNSS is advertised

      *  A DHCPv6 server on the same link advertising IPv6 addresses and
         RDNSS

   o  Results

      *  Fedora 21, Centos 7 and Ubuntu 14.04 get IPv6 address using
         SLAAC only (no address from the DHCPv6 server).

         +  Fedora 21, Centos 7 get RDNSS from both the RAs and the
            DHCPv6 server.  The RDNSS obtained from the router has a
            higher priority though.

         +  Ubuntu 14.04 gets an RDNSS from the router, and a "domain
            search list" information from the DHCPv6 server - but not
            RDNSS information.

      *  MAC OS-X also gets RDNSS from both, IPv6 address using SLAAC
         (no IPv6 address from the DHCPv6 server) but the RDNSS obtained
         from the DHCPv6 server is first (it has a higher priority).
         However, the other obtained from the RAs is also present.

      *  Windows 7 and Windows 8.1 obtain IPv6 addresses using SLAAC and
         RDNSS from the DHCPv6 server.  They do not get IPv6 address




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         from the DHCPv6 server.  Compare the Windows 8.1 behaviour with
         the previous case.

   Case 3: Same as Case 2 but Without a DHCPv6 Server

   o  Set up

      *  One IPv6 Router with M=0, A=1, O=1 and an RDNSS is advertised

      *  no DHCPv6 present

   o  Results

      *  Windows 7 and Windows 8.1 get an IPv6 address using SLAAC but
         they do not get RDNSS information.

      *  MAC OS-X, Fedora 21, Centos 7 and Ubuntu 14.04 get an IPv6
         address using SLAAC and RDNSS from the RAs.

   Case 4: All Flags are Set and a DHCPv6 Server is Present

   o  Set up

      *  One IPv6 Router with M=1, A=1, O=1 and an RDNSS is advertised

      *  A DHCPv6 server on the same link advertising IPv6 addresses and
         RDNSS

   o  Results

      *  Fedora 21 and Centos 7:

         +  They get IPv6 address both from SLAAC and DHCPv6 server.

         +  They get RDNSS both from RAs and DHCPv6 server.

         +  The DNS of the RAs has higher priority.

      *  Ubuntu 14.04:

         +  It gets IPv6 address both using SLAAC and from the DHCPv6
            server.

         +  It gets RDNSS from RAs only.

         +  From the DHCPv6 server it only gets "Domain Search List"
            information, no RDNSS.




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      *  MAC OS-X:

         +  It gets IPv6 addresses both using SLAAC and from the DHCPv6
            server.

         +  It also gets RDNSS both from RAs and the DHCPv6 server.

         +  The DNS server of the DHCPv6 has higher priority.

      *  Windows 7 and Windows 8.1:

         +  They get IPv6 address both from SLAAC and DHCPv6 server.

         +  They get RDNSS only from the DHCPv6 server.

   Case 5: All Flags are Set and There is No DHCPv6 Server is Present

   o  Set up

      *  One IPv6 Router with M=1, A=1, O=1 and an RDNSS is advertised

      *  no DHCPv6 is present

   o  Results

      *  Windows 7 and Windows 8.1 get an IPv6 address using SLAAC but
         no RDNSS information.

      *  MAC OS-X, Fedora 21, Centos 7, Ubuntu 14.04 get an IPv6 address
         using SLAAC and RDNSS from the RAs.

   Case 6: A Prefix is Advertised by RAs but the 'A' flag is not Set

   o  Set up

      *  An IPv6 Router with M=0, A=0 (while a prefix information is
         advertised), O=0 and an RDNSS is advertised.

      *  DHCPv6 is present

   o  Results

      *  Fedora 21, Centos 7, Ubuntu 14.04 and MAC OS-X:

         +  They do not get any IPv6 address (neither from the RAs, nor
            from the DHCPv6).

         +  They get a RDNSS from the router only (not from DHCPv6).



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      *  Windows 8.1

         +  They get IPv6 address and RDNSS from the DHCPv6 server
            ("last resort" behaviour).

         +  They do not get any information (neither IPv6 address not
            RDNSS) from the router.

      *  Windows 7:

         +  They get nothing (neither IPv6 address nor RDNSS) from any
            source (RA or DHCPv6).

A.2.3.  Address/DNS Auto-configuration Behavior of Using Two IPv6 Router
        and a DHCPv6 Server

   these scenarios there are two routers on the same link.  At first,
   only one router is present (resembling the "legitimate router)",
   while the second one joins the link after the clients first
   configured by the RAs of the first router.  Our goal is to examine
   the behaviour of the clients during the interchange of the RAs from
   the two different routers.

   Case 7: Router 1 Advertising M=0, O=0 and RDNSS, and then Router 2
   advertising M=1, O=1 while DHCPv6 is Present

   o  Set up

      *  Initially:

         +  One IPv6 router with M=0, O=0, A=1 and RDNSS advertised and
            15 seconds time interval of the RAs

      *  After a while (when clients are configured by the RAs of the
         above router):

         +  Another IPv6 router with M=1, O=1, no advertised prefix
            information, and 30 seconds time interval of the RAs.

         +  A DHCPv6 server on the same link providing IPv6 addresses
            and RDNSS.

   o  Results

      *  MAC OS-X and Ubuntu 14.04:

         +  Initially they get address and RDNSS from the first router.




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         +  When they receive RAs from the second router, they never get
            any information (IPv6 address or RDNSS) from the DHCPv6
            server.

      *  Windows 7:

         +  Initially they get address from the first router - no RDNSS.

         +  When they receive RAs from the second router, they never get
            any information (IPv6 address or RDNSS) from the DHCPv6
            server.

      *  Fedora 21 and Centos 7:

         +  Initially they get IPv6 address and RDNSS from the RAs of
            the first router. o

         +  When they receive an RA from router 2, they also get an IPv6
            address and RDNSS from the DHCPv6 server while retaining the
            ones (IPv6 address and RDNSS) obtained from the RAs of the
            first router.  The RDNSS obtained from the first router has
            a higher priority than the one obtained from the DHCPv6
            server (probably because it was received first). o

         +  When they receive again RAs from the first router, they
            lose/forget the information (IPv6 address and RDNSS)
            obtained from the DHCPv6 server.

      *  Windows 8.1:

         +  Initially, they get just an IPv6 address from the first
            router 1 - no RDNSS information (since they do not implement
            RFC 6106).

         +  When they receive RAs from the second router, then they also
            get an IPv6 address from the DHCPv6 server, as well as RDNSS
            from it.  They do not lose the IPv6 address obtained by the
            first router using SLAAC.

         +  When they receive RA from the first router, they retain all
            the obtained so far information (there isn't any change).

   Case 8: (Router 2) Initially M=1, O=1 and DHCPv6, then 2nd Router
   (Router 1) Rogue RAs Using M=0, O=0 and RDNSS Provided

   o  Set up

      *  Initially:



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         +  One IPv6 router with M=1, O=1, no advertised prefix
            information, and 30 seconds time interval of the RAs.

         +  A DHCPv6 server on the same link advertising IPv6 addresses
            and RDNSS.

      *  After a while (when clients are configured by the RAs of the
         above router):

         +  Another IPv6 router with M=0, O=0, A=1, RDNSS advertised and
            15 seconds time interval of the RAs.

   o  Results

      *  Fedora 21 and Centos 7:

         +  At first, they get information (IPv6 address and RDNSS) from
            the DHCPv6 server.

         +  When they receive RAs from the second router, they get
            address(es) and RDNSS from these RAs.  At the same time, the
            IPv6 address and the RDNSS obtained from the DHCPv6 server
            are gone.

         +  When they receives again an RA from the first router, they
            perform the DHCPv6 Confirm/Reply procedure and they get an
            IPv6 address and RDNSS from the DHCPv6 server while
            retaining the ones obtained from the RAs of the second
            router.  Moreover, the RDNSS from router 1 has higher
            priority than the one from DHCPv6.

      *  Ubuntu 14.04:

         +  At first, it gets information (IPv6 address and RDNSS) from
            the DHCPv6 server.

         +  When it receives RAs from the second router, it also gets
            information from it, but it does not lose the information
            obtained from the DHCPv6 server.  It retains both.  It only
            gets "Domain Search list" from the DHCPv6 server-no RDNSS
            information.

         +  When it receives RAs from the first router, there is no
            change; it retains all the obtained information.

      *  Windows 7:





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         +  Initially they get IPv6 address and RDNSS from the DHCPv6
            server.

         +  When they get RAs from the second router, they lose this
            information (IPv6 address and RDNSS obtained from the DHCPv6
            server) and they get only SLAAC addresses using the RAs of
            the second router-no RDNSS.

         +  When they receive RAs from the first router again, they get
            RDNSS and IPv6 address from the DHCPv6 server, but they also
            keep the SLAAC addresses.

      *  Windows 8.1:

         +  Initially they get information (IPv6 address and RDNSS) from
            the DHCPv6 server.

         +  When they receive RAs from the second router, they never get
            any information from them.

      *  MAC OS-X:

         +  Initially it gets information (IPv6 address and RDNSS) from
            the DHCPv6 server.

         +  When it gets RAs from the second router, it also gets a
            SLAAC IPv6 address but no RDNSS information from the RAs of
            this router.  It also does not lose any information obtained
            from DHCPv6.

         +  When it gets RAs from the first router again, the situation
            does not change (IPv6 addresses from both the DHCPv6 and
            SLAAC process are retained, but RDNSS information only from
            the DHCPv6 server).

Authors' Addresses

   Bing Liu
   Huawei Technologies
   Q14, Huawei Campus, No.156 Beiqing Road
   Hai-Dian District, Beijing, 100095
   P.R. China

   Email: leo.liubing@huawei.com







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   Sheng Jiang
   Huawei Technologies
   Q14, Huawei Campus, No.156 Beiqing Road
   Hai-Dian District, Beijing, 100095
   P.R. China

   Email: jiangsheng@huawei.com


   Xiangyang Gong
   BUPT University
   No.3 Teaching Building
   Beijing University of Posts and Telecommunications (BUPT)
   No.10 Xi-Tu-Cheng Rd.
   Hai-Dian District, Beijing
   P.R. China

   Email: xygong@bupt.edu.cn


   Wendong Wang
   BUPT University
   No.3 Teaching Building
   Beijing University of Posts and Telecommunications (BUPT)
   No.10 Xi-Tu-Cheng Rd.
   Hai-Dian District, Beijing
   P.R. China

   Email: wdwang@bupt.edu.cn


   Enno Rey
   ERNW GmbH

   Email: erey@ernw.de
















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